1. Field of the Invention
The present invention relates to a laminated LC component, and more particularly, to a laminated LC component for use as a noise filter or the like in a high-frequency electronic circuit.
2. Description of the Related Art
FIGS. 5 and 6 illustrate an example of a conventional laminated LC component of the above-described type. The laminated LC component 1 includes insulating sheets 2 having respective coil conductors 21-28 provided on the surface of the respective insulating sheets 2, insulating sheets 2 having respective capacitor electrodes 31 and 32 disposed on the surface of the respective insulating sheets 2, and a cover sheet 2. These sheets 2 have a rectangular shape.
The coil conductors 21-24 are electrically connected in series through via-holes 33a-33c formed in the insulating sheets 2 so that the connected coil conductors define a helical coil L11. Similarly, the coil conductors 25-28 are electrically connected in series through via-holes 33j-33l formed in insulating sheets 2 so that the connected coil conductors define a helical coil L12. The capacitor electrodes 31 and 32 face each other with the insulating sheet 2 disposed therebetween such that a capacitor C11 is formed thereby. The plurality of capacitor electrodes 31 are electrically connected to one another through via-holes 33e-33h formed in insulating sheets 2.
An end of the coil L11 (more specifically, an end of the coil conductor 24) is electrically connected through a via-hole 33d to the capacitor electrode 31 which functions as one electrode of the capacitor C11. Similarly, an end of the coil L12 (more specifically, an end of the coil conductor 25) is electrically connected through a via-hole 33i to the capacitor electrode 31 which functions as an electrode of the capacitor C11. Both ends 32a and 32b of the capacitor electrode 32 are exposed at the front side and rear side, respectively, of the insulating sheet 2.
The insulating sheets 2 are stacked on one another and fired into the form of a single unitary laminated block 15 as shown in FIG. 6. External input/output electrodes 11 and 12 are formed on the left and right ends, respectively, of the laminated block 15, and external ground electrodes 13a and 13b are formed on the front and rear side surfaces 15c and 15d, respectively. An end of the coil L11 (more specifically, an end of the coil conductor 21) is electrically connected to the external input/output electrode 11 and an end of the coil L12 (more specifically, an end of the coil conductor 28) is electrically connected to the external input/output electrode 12. The ends 32a and 32b of the capacitor electrodes 32 are electrically connected to the external ground electrodes 13a and 13b, respectively. FIG. 7 is an equivalent electric circuit diagram of the laminated LC component 1 obtained in the above-described manner.
In the conventional laminated LC component 1, external ground electrodes 13a and 13b are provided only on the front and rear side surfaces 15c and 15d. As a result, the mounting surface of the laminated type LC component 1 is limited to either the upper side surface 15a or the lower side surface 15b of the laminated block 15. That is, the LC component 1 has directivity in terms of mounting orientation.
One possible technique to solve the above problem associated with the mounting directivity is to form an external ground electrode into the form of a band circumferentially extending over the four side surfaces of the laminated block 15. However, when the external ground electrode is simply formed along the entire circumference over the side surfaces 15a-15d, the ends 32a and 32b of the capacitor ground electrode 32 of the capacitor C11 formed in the laminated block 15 are exposed only at the side surfaces 15c and 15d of the laminated block 15 and thus, the length of the conductor path between the external ground electrode to the capacitor electrode 32 varies depending on which of the side surfaces 15a-15d is used as the mounting surface. Therefore, the high-frequency characteristics of the LC component 1 vary depending on the mounting surface that is used. That is, the LC component 1 has directivity in terms of the component characteristics.
Furthermore, because the laminated block 15 has a rectangular shape in lateral cross section, the external ground electrode formed along the entire circumference over the side surfaces 15a-15d has different shapes between the side surfaces 15a, 15b and the side surfaces 15c, 15d. Therefore, when the external ground electrode is produced, two different sets of jigs or tools are required. This results in a reduction in productivity efficiency.
To overcome the problems described above, preferred embodiments of the present invention provide a laminated LC component having no directivity in terms of mounting and component characteristics.
According to one preferred embodiment of the present invention, a laminated LC component includes a laminated block having a substantially square shape in lateral cross section and a plurality of insulating layers, a plurality of coil conductors, and a plurality of capacitor electrodes, a coil formed by electrically connecting the plurality of coil conductors, the coil having an axis that is substantially parallel to a stacking direction of the laminated block and also substantially parallel to the mounting surface of the laminated block; a capacitor defined by the plurality of capacitor electrodes, the capacitor being electrically connected to the coil, an external input/output electrode disposed on an end of the laminated block, and an external ground electrode having a band shape and extending along a circumference over four side surfaces of the laminated block, wherein the ends of the capacitor electrode, at the ground side, of the capacitor are exposed at the four respective side surfaces of the laminated block and the ends of the capacitor electrode are electrically connected, at the four side surfaces, to the external ground electrode, and wherein any of the four side surfaces is arranged to be usable as a mounting surface.
In the laminated type LC component constructed in the above-described manner, because the external ground electrode has a band shape extending along the circumference of the laminated block over the four side surfaces, there is no directivity in terms of mounting. Furthermore, because the ends of the capacitor ground electrode of the capacitor are electrically connected, at the four respective side surfaces, to the external ground electrode, the length of the conductor path from a ground pattern on a circuit board to the capacitor ground electrode via the external ground electrode becomes substantially equal whichever of the four side surfaces is used as the mounting surface. Therefore, the LC component has substantially equal high-frequency characteristics regardless of which of the four side surfaces of the laminated block is used as the mounting surface. That is, the LC component has no directivity in terms of the component characteristics.